Work holding, clamping and centering devices for machine tools



Aug. 17, 1965 O. ROGG WORK HOLDING, CLAMPING AND CENTERING DEVICES FORMACHINE TOOLS Filed Jan. 12. 1962 6 Sheets-Sheet 1 Mauro Otto R099 Byflax/L44 f. fweu his HTTORNEY ROGG 3,200,711 WORK HOLDING, CLAMPING ANDCENTERING DEVICES FOR MACHINE TOOLS Filed Jan. 12, 1962 6 Sheets-Sheet 22/ 20% \Ii/ 26 3/ A 29 1 r I 24 J I )7; 13 31-, 26 7;; U

I II 30 I 2 221111 I2 24 l mm \\\\\a 2;

JN VEN TOR Otto R999 BS 4! his ATTORNEY O. ROGG Aug. 17, 1965 200,711WORK HOLDING, CLAMPING AND CENTERING DEVICES FOR MACHINE TOOLS 6Sheets-Sheet 3 Filed Jan. 12, 1962 Otto R099 Aug. 17, 1965 o. ROGG3,200,711 WORK HOLDING, CLAMPING AND CENTERING DEVICES FOR MACHINE TOOLSFiled Jan. 12, 1962 6 Sheets-Sheet 4 was JIWE NT 0R Otto R099 71-21![fir/w his ATTORN E Y O. ROGG PING AND Aug. 17, 1965.

3,200,711 WORK HOLDING, CLAM CENTERING DEVICES FOR MACHINE TOOLS 6Sheets-Sheet 5 Filed Jan. 12, 1962 v 33 mm mm 2 R R A, 1 2 VII... d T.N0 M A J a J S a F 6mm 1 3 3 5 B 2 m 9 .Il a a a J 35. 0 1 9 .M 2,21. q2 a a a a an n/ M N 4 2 H\ l v H .6 2 4. a l w 8 52 2 1 2 4 2 2 2 5 2 2W .4 a 2 2 5 2 mm 2 Aug. 17,- 1965 O. ROGG WORK HOLDING, CLAMPING ANDCENTERING DEVICES FOR MACHINE TOOLS Filed Jan. 12, 1962 6 Sheets-Sheet 6Fig. 5 JNVENTOR Otto R039 T R-44:1 fl r his ATTORNEY Unitcd StatesPatent 3,200,711 WORK HOLDING, CLAMPTNG AND CENTERING DEVICES FORMACHINE T0015 Otto Rogg, Munich, Germany, assignor to Carl Hurth,Munich, Germany Filed Jan. 12, 1962, Ser. No. 165,844 Claims priority,application Germany, Jan. 13, 1%1, H 41,454; Jan. 27, 1961, H 41,560 8Claims. (Cl. 90-4) The present invention relates to machine tools ingeneral, and more particularly to improvements in work holding,retaining, clamping and centering devices for use in machine tools.Still more particularly, the invention relates to work retaining,clamping and centering devices which are especially suited for use ingear shaping apparatus, such as machines for shaving the teeth or" spurgears, helical gears and the like.

As is known, the output of a machine tool is increased if the durationof contact between a workpiece and the shaping tool is reduced, i.e. ifa tool may remove thick shavings during each pass with respect to theworkpiece. Such operation renders it necessary to mount the tool and theworkpiece with utmost precision and to properly support and retain theworkpiece so that the latter remains strongly clamped and is accuratelycentered during repeated contact with the tool. It is also known thatthe work retaining headstock and/ or the tailstock of a gear shapingmachine must be mounted in its ways in such a way that it has at leastsome, even very slight, play during movement toward or away from theworkpiece. This play is very undesirable when the machine tool isutilized for precision treatment of workpieces, eg for shaving the teethof gears and the like, because even minimal tolerances will causeundesirable deviations in the configuration and/ or spacing of the gearteeth.

Accordingly, it is an important object of the present invention toprovide an improved arrangement which will automatically clamp the workretaining tailstock or headstock of a machine tool to its support orcolumn when the work retaining element is called upon to retain aworkpiece, and which will automatically release the element when itbecomes necessary to remove the workpiece from or to reset the workpiecein the machine tool.

Another object of the invention is to provide a clamping arrangement ofthe just outlined characteristics which will automatically increase theclamping pressure upon the work retaining element in response to advanceof the element toward the workpiece.

A further object of the invention is to provide a clamping arrangementof the above described type whose clamping force may be determined andchanged before the element is set in motion with respect to its support.

An additional object of the invention is to provide a machine tool inwhich the work retaining element may be reciprocated and clamped by asingle mechanically, hydraulically, pneumatically, magnetically orelectrically actuated mechanism.

A concomitant object of the invention is to provide an improved workcentering device which is especially suited for use in connection with awork retaining tailstock or headstock cooperating with a clampingarrangement of the above outlined characteristics, and which is intendedfor retention and centering of apertured workpieces, such as spur gearsand the like having through bores or apertures into and through whichthe component parts of the improved device may extend when the device isin actual use.

Still another object of the invention is to provide a work centeringdevice of the just outlined characteristics which is especially suitedfor use in gear shaving machines azaa'in Fatented Aug. 17, 1965 andwhich may be actuated to center or to release a workpiece in a fullyautomatic way and in rhythm with other operations of the machine tool.

A further object of the invention is to provide a machine tool,particularly a gear shaping machine, which embodies a clampingarrangement and a cooperating centering device of the above outlinedcharacteristics.

With the above objects in view, the invention resides in the provisionof a machine tool, particularly of a machine tool for treatment ofapertured workpieces, such as spur gears and helical gears, whichcomprises a frame, a support provided on the frame and having elongatedways, a retaining element (e.g. a headstock) reciprocably mounted in theways of the support, a spindle supported by the frame and having an axisparallel with the longitudinal direction of the ways, a spindle sleevesupported by the retaining element and coaxial with the spindle, and acombined reciprocating and clamping arrangement for the retainingelement. This arrangement comprises a motive-force-transmitting member(eg. a link, a threaded spindle, a piston rod, or the like) which isoperatively connected with the retaining element and is movable indirections enclosing an acute angle with the longitudinal direction ofthe ways on the support so that the force transmitted by this member tothe retaining element includes a reciprocating component which isparallel with the longitudinal direction of the ways and a secondcomponent which is perpendicular to the longitudinal direction of theways. This second component clamps the retaining element to its supportwhen the retaining element is moved in a first direction, and thissecond component automatically unclamps the retaining element from itssupport when the element is moved in the opposite direction.

Another important feature of my invention resides in the provision of awork centering and holding device which is mounted in part in theretaining element and is in part supported by the frame. This devicecomprises a reciprocable center which is axially movable in the spindleor in the spindle sleeve, and a collet which is secured to the spindlesleeve or to the spindle so as to en gage with and to be separable fromthe center. The collet comprises substantially radially movablecenter-engaging claws and defines an internal space .for the center.This center may spread the claws of the collet into centering engagementwith the wall bounding the aperture of the workpiece or with a guidesleeve which is mounted in a special work support carried by thespindie. In the latter instance, the center is rigid with a mandrelwhich has a portion tightly receivable in the aperture of the workpiece.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following detailed description of certainspecific embodiments with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a gear shaping machine which comprises awork retaining element and a work centering device embodying one form ofmy invention;

FIG. 1a is a side elevational chine shown in FIG. 1;

FIG. 2 is an enlarged fragmentary vertical section as seen in thedirection of arrows from the line IIII of FIG. 1 or P163, showing themanner in which the main shaft of the machine transmits rotary motion tothe tool spindle;

FIG. 3 is a horizontal section as seen in the direction of arrows fromthe III-III of FIG. 2;

view of a detail of the maaaoomr FIG. 4 is an enlarged vertical sectionas seen in the direction of arrows from the line IVIV of FIG. 1, showingone form of the improved arrangement for reciprocating and clamping thework retaining element of the gear shaping machine;

FiG. 4a is a fragmentary partly elevational and partly sectional view ofa reciprocating arrangement which constitutes a slight modification ofthe arrangement shown in FIG. 4;

FIG. 5 is a similar vertical section showing a modified reciprocatingand clamping arrangement;

FIG. 6 is a fragmentary schematic view of a manually operable mechanicalreciprocating and clamping arrangement;

FIG. 7 is an enlarged fragmentary vertical section through a portion ofthe retaining element shown in 'FIG. 5, illustrating one form of mynovel work holding and clamping device;

FIG. 8 is a similar vertical section showing a modified work holding andclamping device; and

FIG. 9 is a fragmentary side elevational view of a composite colletwhich forms part of the device shown in FIG. 8.

Referring now in greater detail to the illustrated embodiments, andfirst to FlGS. l to 3, there is shown a gear shaping machine whichcomprises a frame 1th having a pair of spaced vertical guides ltll, 11a(see FIG. 3) for a reciprocable hollow tool slide 12, and a pair ofspaced horizontal guides 13, 13a for a reciprocable hollow work slide14;. The guides 11, 11a and 13, 13a are provided on the vertical frontwall of the frame lit to control the direction of reciprocatory movementof the slides 12, 14 in such a way that these slides travel in pathswhich enclose right angles with each other. The frame ll) defines aninternal chamber which accommodates a withdrawable shavings-collectingpan or tray 15.

The upper portion of the tool slide 12 receives an electric motor 18which operates a V-belt drive including a pair of pulleys 19a, 19!) andbelt means 19. The pulley 1% drives a shaft 29 whose front end portioncarries a spur gear 21 forming part of a speed change gear whichincludes a second spur gear 21a meshing with the gear 21, a shaft 22which is driven by the gear 21a, and a bevel gear 23 which is driven bythe shaft 22. The speed change gear determines the rpm. of the tool, Thebevel gear 23 drives a bevel gear 230, which is mounted on and rotates ahorizontal main shaft 24 (see particularly FIGS. 2 and 3) whoseright-hand portion projects from the tool slide 12 and into a turnabletool holder or carrier 25. The latter is mounted on the tool slide 1?.and is turnable about the axis of the main shaft 24. This tool holdermay be arrested in one or more angular positions of adjustment withrespect to the slide 12.

The main shaft 24 carries at its right-hand end a bevel gear 26 whichmates with a bevel gear 26a mounted at one end of a shaft 27 Which isrotatably mounted in the tool holder and whose other end carries apinion 28. This pinion meshes with a spur gear Zita which is mounted ona spindle 29 for the substantially worm-shaped tool 36. In theembodiment of FIGS. 1 to 3, the tool 3% is assumed to be a hob. That endportion of the tool 3t) which is turned away from the spindle 29 isturnably supported in a suitable backrest Sl'la (see FlG. 3).

The left-hand end of the main shaft 24 removably carries one spur gear31 (see FIGS. 1a, 2 and 3) of a gear train or group constituting anindex change gear which also includes gears 31a, 31b, 31c, the lattermounted on a horizontal shaft 32 forming part of another groupconstituting a reversing gear. This reversing gear includes a pair ofspaced bevel gears 33, 34 which are freely rotatable on the shaft 32 andwhich are in permanent mesh with a driven bevel gear 35 mounted at theupper end of a splined shaft 36a, and a clutch sleeve 36 which is drivenby and is slidable along the shaft 32. Each axial end of this sleeve isprovided with a set of teeth so that Cir the sleeve may alternatelyengage with complementary teeth of the gear 33 or 3 in order to drivethe bevel gear and the splined shaft 36a in clockwise or anticlockwisedirection. The control lever which shifts the sleeve 36 along the shaft32 into engagement with the gear 33 or 34 is not shown in the drawings.The purpose of the reversing gear is to drive the work spindle 50 inclockwise or anticlockwise direction.

The lower end of the splined shaft 36a extends from the underside of thetool slide 12 and into a stationary housing 37 which is fixed to thebedplate 47 of the machine. The housing 37 accommodates an internallysplined rotary cylinder 38 which receives the splined lower end portionof the shaft 36a and transmits rotary motion to a bevel gear 39 meshingwith a bevel gear 39a mounted at the left-hand end of a Worm shaft ill.The splined 36a and the cylinder 35 form part of the driving connectionbetween the main shaft 24 and the work spindle 551 Since the cylinder 38is rotatable in the stationary housing 37, and since the splined shaft36a is free to perform axial movements with respect to the cylinder 33,the connection between the reversing gear and the worm shaft as is notinterrupted when the tool slide 12 is caused to reciprocate in itsguides 11, 11a.

The tool slide 12 is reciprocated in the following way:

The worm shaft 46 carries a worm 4-1 which is located in the housing 37and which meshes With a worm wheel 42 mounted on the input shaft 42a ofa feed change gear. This feed change gear further includes a gear train43, 43a, 43b, 43s, the latter mounted on and driving a worm shaft 43dthrough a suitable clutch (not shown). The worm on the shaft 43d mesheswith a Worm wheel 44 mounted at the lower end of a vertical feed spindleor screw 45. The upper portion of the screw 4-5 projects into the toolslide 12 and meshes with an internally threaded spindle nut 46 which isrigidly mounted in the slide 12 so that rotary movements of the screw 45in clockwise or anticlockwise direction will compel the slide 12 to moveup or down in its guides 11, 11a.

The right-hand portion 46a of the worm shaft 40 is splined and projectsinto the lower part of the work slide 14 where it meshes with aninternally splined worm 4% so that this worm may perform axial movementswith respect to but is compelled to share all angular movements of theshaft 49. The worm 4-8 drives a worm wheel 49 which is provided at thelower end of the work spindle St The head or nose 51 of the work spindleis located at a level above the upper side of the Work slide 14 andindirectly supports the workpiece 52. in a novel manner which will bedescribed in connection with FIGS. 7 to 9.

The work slide 14 is engaged by a horizontal retaining rail d ll whichis fixed to the bedplate 47 so as to prevent any lateral play but topermit horizontal reciprocatory movements of the slide i l along theguides 13, 13a. The slide 14 carries a support or column 53 which isprovided with vertical ways 54a. This slide and support together serveas a supporting arrangement for a work retaining element in the form ofa headstock 54- whose novel construction, mounting and operation will bedescribed in connection with FIGS. 4 to 6.

The gears and eventually the motor for effecting feed movements of thework slide 14 along the guides 13, 13a are accommodated in a gear box 61which is mounted on a supporting surface 59 of the frame it) rearwardlyof the column 53.

The above described parts of the machine shown in FIGS. 1 to 3 aredisclosed and claimed in my copending application Serial No. 155,042 forGear Shaping Machine to which reference may be had, if necessary. Theseparts were described solely for the purpose of facilitating theunderstanding of the novel manner in which the element 54 may be movedalong and clamped to its support 53 (FIGS. 4 to 6), and of the novelmanner in which the workpiece 52 may be held and centered between thespindle nose 51 and the element 54 (FIGS. 7 to 9).

Referring to FIG. 4, it will be seen that the support or column 53 is ahollow structure which defines an internal compartment 53a and whosefront wall 53b is formed with a cutout or window 53c adjacent to asimilar cutout or window 540 provided in the rear wall 54b of the workretaining element or headstock 54. This headstock is also hollow anddefines an internal compartment 54d which communicates with thecompartment 53a through the windows 53c, 540.

The improved clamping and reciprocating arrangement for the headstock 54is accommodated in the compartments 53. 1, 54d and comprises adouble-acting fluid-operated (preferably hydraulic) cylinder 122 whoselower end is pivotally secured to the work slide 14 by a horizontalpivot pin 126 which is received in an apcrturcd bracket 122a rigid withthe cylinder. This cylinder receives a reciprocable piston 123 whichdivides its interior into an upper cylinder chamber 124 and into a lowercylinder chamber 125. The piston 123 is connected with a swingableelongated motive force transmitting rod 127 which is slidably guided inthe upper end wall of the cylinder 122 and whose upper end isarticulately secured to a horizontal pivot pin 128 mounted in theheadstock 54. It will be noted that the piston rod 127 extends throughthe windows 53c, 540. The cylinder chambers 124, 125 respectivelycommunicate with conduits 124a, 125a which are connected with a pump125b or another source of pressure fluid. Suitable control valve means1250 are provided to regulate the inflow and outflow of pressure fluidthrough the conduits 124a, 125a. Such valve means may be of anyconventional design and may be regulated in a fully automatic way, forexample, by the control system of the gear shaping machine or by thecontrol system of the work centering device, and the exact constructionthereof is well known to men skilled in the art.

The workpiece 52 (shown in FIGS. 1, 7 and 8) is held between the nose 51of the work spindle 5i) and a spindle sleeve 116 which is mounted in theheadstock 5d.

The axis of the reciprocating means including the cylinder 122, thepiston 123 and the rod 127 is inclined with respect to the direction inwhich the headstock 54 is slidable in its ways 54a so that this axisencloses with the axis of the spindle sleeve 116 a downwardly openingacute angle alpha. Consequently, when the control system associated withthe cylinder 122 admits pressure fluid to the upper chamber 124 andpermits pressure fluid to escape from the lower chamber 125, the force131 with which the swingable piston rod 127 tends to move the headstock54 in downward direction has a vertical reciprocating component 129which is parallel with the direction of downward movement of theheadstock (i.e. with the longitudinal direction of the ways 54a) andwhich actually moves this headstock in the ways 54a, and a horizontalclamping component 131 which tends to move the headstock against thefront wall 53b and thereby clamps the headstock against the column 53.The component 131 is substantially perpendicular to the longitudinaldirection of the ways 54a.

If it is desired to move the headstock 54 in upward direction, i.e. topermit removal of the workpiece 52, fluid filling the chamber 124 ispermitted to escape through the conduit 124a while the other conduit125a admits pressure fluid to the lower chamber 125 so that the motiveforce transmitted by the piston rod 127 to the headstock 54 has anupwardly directed reciprocating component which actually moves theheadstock in its ways 54a and a leftwardly directed unclamping componentwhich tends to separate the headstock from the front wall 53b. When theheadstock 54 slides in its ways 54a, the bracket 122a and the piston rod127 respectively pivot or swing about the pins 126, 123.

The component 129 of the force 1351 indicated in FIG. 4 preventsmovement of the spindle sleeve 116 upwardly and away from the spindlenose 51 when the workpiece 52 is subjected to the action of the tool3rd. It will be readily understood that the clamping component 131 ofthe force 1129 increases proportionally with the force 129 which, ofcourse, is hi hly desirable during-a gear shaving operation. Since thepin 126 is secured to the Work slide 14, the reciprocating means 122,123, 127 actually presses the column 53 against the slide 14- when theupper chamber 124, receives pressure fluid. The unclamping action of thepiston rod 127 is fully automatic as soon as the lower chamber isconnected with the source of pressure fluid.

The cylinder 122 is accessible through an aperture 53c provided in theupper end wall 53 of the column 53, and this aperture is normally sealedby a detachable cover plate or lid 53g.

1G. 5 illustrates a modified reciprocating and clamping arrangementwhich is analogous to that shown in FIG. 4. The slightly modified hollowsupport or column 153 is provided with an internal compartment 153awhich accommodates a fixed double-acting cylinder 135. The lower end ofthis cylinder is fixed to the bottom end Wall 1531: of the column 153 sothat its conduit 135a extends into the interior of the hollow work slide14, ie the cylinder is not secured to the work slide 1 but solely to thecolumn 153. The cylinder 135 receives a reciprocable piston 136 whichdivides its interior into an upper cylinder chamber 135d and a lowercylinder chamber 135a The chambers 1350, 135d respectively communicatewith the conduits 1351;, 1335b which are connected to a suitable sourceof pressure fluid (preferably oil) through control valve means of thetype mentioned in connection with FIG. 4. The piston 136 is connectedwith a piston rod 137 whose upper end is bolted to a pusher 138 which isslidably guided in vertical ways 139 provided on a detachable panel ordoor 149 secured to the apertured rear wall 1531' of the column 153. Theways 139 and the cylinder 135 insure that the piston rod 137reciprocates in vertical directions to rock a two-armed lever 14-2through a link 1% which is resepectively pivoted to the right-hand armof the lever 142 (pin 146a) and to the pusher 138 (pin 14%). The lever142 is rockable about a horizontal pin 141 which is fixed to the column153, and the left-hand arm of this lever extends through aligned windows1530, 54c, the former provided in the front wall 1531: of the column 153and the latter provided in the rear wall 54b of the work retainingheadstock 54. The free end of the left-hand arm of the lever 142 isarticulately connected to a swinga'ble motive force transmitting link147 by means of a pivot pin C, and a similar pivot pin 145a connects thelower end of the link 147 with a bracket 542 provided in the internalcompartment 54d. The plane common to the axes of the horizontal pins145e, 145a encloses with the longitudinal direction of the ways 54a 21downwardly opening acute angle beta so that the motive force 144transmitted by the link 147 to the headstock 54 (and acting in thecommon plane of the pins 145e, 145a) when the lower cylinder chamber135a receives pressure fluid through the conduit 135a will have adownwardly directed reciprocating component 1 13 which actually movesthe headstock in its ways 54a, and a rightwardly directed clampingcomponent 145 which tends to clamp the headstock to the front wall 153])of the column 153.

The inclination of the force 1 14 may be changed so as to change themagnitude of the clamping component 145. In the embodiment of FIG. 5,the means for changing the magnitude of the clamping component 145comprises an elongated slot 145!) formed in the left-hand arm of thelever 14-2, and this slot permits adjustments in the position of thepivot pin 1 15c so that the inclination of the plane common to the pins145a, 145a and hence the inclination of the force 14 1 may be changed.Of course means is provided for maintaining the pin 145C in its slot1d-5b in a plurality of selected positions each of which corresponds toa different clamping force.

It is equally possible to fix the pin 146a to the column 153 and toconnect the reciprocating means 122 123, 127 of FIG. 4 wit-h anintermediate portion of the lever M2, i.e. at a point between the pins145, Men. In such con structions, the pin M1, the block and the link Mdmay be dispensed with, and the ever 142 then acts as a onearmed leverwhich pivots about the pine i i-ea to transmit motion to the headstock54 (see FIG. 4a).

FIG. 6 illustrates a slightly modified reciprocating and clamping meanswhich is analogous to that of FIG. 4, excepting that the fluid-operatedmeans 122, E23 127 is replaced by a mechanical reciprocating meansincluding a threaded motive force transmitting spindle 27 and meansincluding a manually turnable crank 12% for shifting the spindle 127'and for thereby reciprocating the headstock S4 in its ways 54a. It willbe readily understood that the crank 1270' may be replaced by a suitablereversible electric or hydraulic motor and that such motor may bestarted or arrested from the control panel in rhythm with otheroperations of the machine. It is equally possible to replace thefluid-operated reciprocating means 122, 123, 127 (FIG. 4) or 135, 136,137 (FIG. 5) by a manually actuatable or motor-driven mechanical system,eg by a threaded spindle Which is coupled to the pin 128 of FIG. 4 or tothe pin mob of FIG. 5.

As is well known in the art, the headstock 54 must have at least someplay in its ways 54a in order to be rapidly shiftable toward and awayfrom the spindle nose 51. This play is highly undesirable once theheadstock is moved to its operative or work-clamping position, and theimportant advantage of the arrangements shown in FIGS. 4 to 6 is thatthey eliminate any, even slightest, play of the headstock 54 in a fullyautomatic way while at the same time serving as a means forreciprocating the headstock in the ways 54a.

Heretofore, the means for reciprocating and for clamping the headstockconstituted two separate entities, i.e. the headstock was moved in itsWays by a first mechanism and, when in operative position, was clampedto its support by a second mechanism, egg. by clamping screws or byhydraulic clamping apparatus. As far as I am informed at this time, thepresent invention provides for the first time an arrangement which iscapable of reciprocating and of simultaneously clamping or unclampingthe headstock merely by mounting one or more components of thereciprocating means in such a way that the direction of their actionencloses an acute angle with the longitudinal direction of the ways inwhich the work retaining headstock is supposed to move and by arrangingthe headstock in such a way that it moves in a direction to increasethis angle when it should move toward and into direct or indirectretaining engagement with the workpiece The vertical component 129 (FIG.4) or 143 (FIG. 5) of the force transmitted to the headstock exerts aretaining force upon the workpiece, whereas the horizontal component 131or 145 exerts a clamping force upon the headstock to hold it against thecolumn 53 or I53.

in a machine tool in which the column 53 or 153 is mounted directly onor forms part of the slide M, the reciprocating means 122, 123, 127 or135, 136, 137 also serves as a means for holding the column against theslide whenever the headstock is moved in a direction to retain aworkpiece. In such instances, the pin 126 of FIG. 4 or the lower part ofthe cylinder 13-5 shown in FIG. 5 is mounted directly in the machineframe. For example, FIG. 6 shows that the column 53 is mounted on theslide.

Referring to FIG. 7, there is shown a work holding and centering deviceincluding a substantially bell-shaped work support 22d which rests onand is secured to the spindle nose 51 (see FIG. 1). The workpiece 52 isassumed to be a spur gear which is to be shaped by the tool 36, and thisworkpiece rests on the top face of the support 22d so that its bore oraperture is coaxially aligned with the bore 22% of the support The bore22% accommodates a work arbor 221 which latter is reciprocable in theaxial direction thereof (arrow 221a) so that it may 8 penetrate throughthe bore 52a. The means for reciprocating the arbor 221 may assume theform of a manually operable or a motor driven device or a hydraulicchuck motor which is schematically shown in FIG. 5. The hydraulic chuckmotor comprises a piston 391 which is reciprocable in the direction ofthe arrow 221a (FIG. 7) in a hydraulic cylinder 362. The piston iscontrolled by valve means 393 which are connected with the hydrauliccylinder by conduits 304, Edda, 34195, 305a and with a pump 596 by aconduit 397. The inflow of pressure fluid is shown with arrow 3% and theoutflow is shown with arrow 309. A sleeve 310 connects the immovableconduits 3M, 3% with the rotary cylinder 3592 and conduits Sit la,Sit-5a. The upper end portion of the arbor 221i assumes the form of aplunger head or center 2232 which is bounded by a cylindrical surface,by an upper conical surface 223 and by a lower conical surface 224.

The spindle sleeve 116 is rotatable in the headstock 54 and is coaxiallyaligned with the support 22% The mounting of the spindle sleeve 116 issuch that it may take up axial stresses. The lower end portion of thisspindle sleeve carries a collet 225 whose fingers or claws 225a aremovable radially inwardly and outwardly with respect to the axis of thespindle sleeve 116. This collet defines an internal space 234 which isadapted to receive the center 222 and whose lower end is bounded by aconical surface 225]) which is complementary to the lower conicalsurface 224 of the center.

The central bore of the spindle sleeve 116 receives a centering tube 226which is axially reciprocable therein and whose lower end portionextends into the bore of the collet 225. It will be noted that the lowerend of the centering tube 226 is provided with an internal conicalsurface 223a which is complementary to the upper conical surface 223 ofthe center 2232. The means for biasing the tube 226 into the collet 225so that its conical internally threaded upper end portion of the spindlesle ve 115. The bias of the spring 227 may be changed by turning theplug 227a with respect to the spindle sleeve. The maximum stroke of thetube 226 is determined by an elongated bar or bolt 223 whose upper endportion is screwed into the plug 227:: and whose lower end portion formsa slotted head 222%: received in an enlarged cortion of the coaxial borein the tube 226 above the conical surface 22312. If the operator desiresto change the stroke of the tube 226, he unscrews the plug 227a andwithdraws the tube 226 with the bolt 228 from the bore of the spindlesleeve 116 so that he may gain access to the slotted head 2280. Thespindle sleeve 116 is rotatable in thrust bearings 116a provided in theheadstock 54.

An annular stripper or stop 239 is adjacent to the upper end face of theworkpiece S2, and the outer diameter of this stripper is suficientlysmall to permit proper engagement between the teeth 52b of the workpieceand the what larger than the diameter diameter of the bore 23% is alsolarger than the diameter of the center 222 so that the latter is free topass therethrough. In fact, the diameter of the bore 239a is somewhatlarger than the outer diameter of the lower end portion of the collet225 formed by the claws 225a so that these claws may move slightly apartwhen received in the bore 239a. The stripper 239 is mounted on ahorizontal arm 229 which is secured to the lower end of a bolt 230 andthis bolt is vertically slidably received in a carrier or block 232fixed to the column 153. As shown, the head 230a of the bolt 23% isbiased in upward direction by a helical spring 231 which is received inan enlarged portion of the bore for the bolt 23% so that the spring 231tends to lift the arm 229 and the stripper 239 above and away from theupper end face of the workpiece 52. The arm 229 is prevented fromturning about the axis of the bolt 23% by a stud 233 which isreciprocable in a vertical bore of the block 232. The stud 233constitutes an optional feature of my invention since it is alsopossible to utilize a swingable arm 229, if desired. The arrangement issuch that the stripper 239 is free to perform axial movements in therange of a few millimeters with respect to the workpiece 52 when thecollet 225 assumes a position at a level above that shown in FIG. 7,i.e. when the shoulders 235 of the claws 225a are spaced from the upperside of the stripper 239. This stripper is detachably secured to its arm229 by a ring nut 22% or the like.

The device of FIG. 7 is operated as follows:

In the first step, i.e. when the headstock 54 is vertically spaced fromthe support 220, the operator or a suitable mechanism places theworkpiece 52 onto the upper end face of the support 229. In the nextstep, the arbor 221 is caused to move upwardly through the bore 52a andinto the collet 225 so that the center 222 move the claws 225a apart andpenetrates into the internal space 234 whereby the claws 225a are freeto return radially inwardly and engage the lower conical surface 224 ofthe center 222. At the same time, the upper conical surface 223 movesinto abutment with the conical surface 223a of the centering tube 226 sothat this tube yields against the bias of the spring 227 and is axiallydisplaced in the bore of the spindle sleeve 116.

In the next step, the two-armed lever 142 and the link 147 bring about adownward displacement of the headstock 54 in the ways 54a So that thearbor 221 and the collet 225 are also caused to move downwardly wherebyportions of the claws 225 of the collet enter the bore 239a of thestripper 239 and penetrate into the bore 52a of the workpiece 52. Thedownward movement of the headstock 54 is arrested before the downwardlyoriented shoulders 235 of the claws 225a engage the upper side of thestripper 239.

In the final step, the operator causes the arbor 221 to move downwardlywith respect to the headstock 54 whereby the lower conical surface 224of the center 222 spreads the claws 225a and causes these claws toengage the wall bounding the bore 52a in the workpiece 52 and to bringabout a preliminary centering of the workpiece. As the arbor 221continues its downward movement, it entrains the collet 225 and movesthe shoulders 235 into abutment with the upper side of the stripper 239so that the latter begins to participate in axial movement of the arbor221 against the bias of the spring 231 and is moved into faceto-faceabutment with the workpiece 52. The conical surface 224 of the center222 now exerts a very strong spreading action upon and forces the claws225a into abutment with the wall bounding the bore 52a so that any, evenminimal, play between the workpiece 52 and the collet 225 is preventedand that the collet is held against any movements with respect to thesupport 220 or the spindle nose 51. The stripper 239 prevents furtherdownward movement of the arbor 221 as soon as its underside comes intoabutment with the upper side of the workpiece 52, and this stripper thentransmits axial holding pressure to the workpiece.

When the gear shaping operation is completed, the operator causes thearbor 221 to move upwardly and thereupon lifts the headstock 54 so as towithdraw the claws 225a from the bores 52a and 239a and to thereuponwithdraw the center 222 from the collet 225. The workpiece may be takenoff the support 226 as soon as the arbor 221 is withdrawn into thesupport 220. The spring 231 automatically lifts the stripper 239 ofi theworkpiece when the shoulders 235 are moved away from the stripper.

The support 229 may be removed so that the workpiece 52 may restdirectly on the spindle nose 51.

Referring finally to FIGS. 8 and 9, there is shown a somewhat modifiedwork holding and centering device in which a slightly different collet245 is mounted on the arbor 244 and is adapted to cooperate with amandrel 24d, the latter having a tight sliding fit with the Wallbounding the bore 52a of the workpiece 52. The internally threaded lowerend portion of the collet 245 is screwed onto a shank 244a which formsan upwardly projecting extension of the arbor 244, and the upper endportion of the collet is formed with upwardly opening T-shaped slots 246(see FIG. 9) each of which accommodates a detachable claw 247. Theseclaws are pressed radially inwardly by an elastic ring 248. The upperend portion of the mandrel 246 is coaxially connected to the spindlesleeve 116 and its lower end portion 241 terminates in a cylindricalcenter or head 242 bounded by an upper conical surface 243 and by alower conical surface 2430. The center 242 is extendable into theinterior of a modified work support 22th which is fixed to the spindlenose 51 and which may accommodate the collet 245 so that the lowerconical surface 243a spreads the claws 247 against the bias of the ring248 by engaging the internal conical surfaces 247a of these claws beforepenetrating into the internal space 245a of the collet to assume theposition of FIG. 8.

The support 220' receives a guide sleeve 250 which is mounted in anantifriction bearing 249 and which is formed with a bore 251 adapted toreceive the claws 247. As shown in FIG. 8, the rolling elements or ballsof the bearing 249 are received in a suitable cage which surrounds thesleeve 250. These rolling elements are received in the support 22%without any or with negligible play. Of course, it is equally possibleto replace the bearing 249 by a tightly fitted cylindrical bushing orthe like, as long as the sleeve is properly guided in its support 220'without any or with minimal lateral play and is permitted to performlimited axial movements in this support. The sleeve 250 is located abovea retaining ring 253 which is mounted in the lower end portion of thesupport 220 and which is formed with suitable recesses for springs 252which tend to move the sleeve 250 in upward direction so that the sleevenormally abuts against an internal shoulder 22th: of the support 220.

The arrangement of FIGS. 8 and 9 also comprises an annular stripper orstop 254 which is mounted on an arm 255 and which is normally biasedaway from the upper end face of the workpiece 52 by one or more springs255a which are mounted in the arm 255. As shown, the stripper 254 haslimited freedom of axial movement with respect to the arm 255.

When the workpiece 52 is placed onto the support 220, the headstock 54is caused to move in downward direction so that the center 242 of themandrel 240 penetrates through the bore of the stripper 254, through thebore 52:: of the workpiece 52, through the bore 266 at the upper end ofthe support 220' and that its lower conical surface 243a engages theupper conical surfaces 247s of the claws 247 whereby the claws arecaused to move apart against the bias of the elastic ring 248 and thecenter 242 penetrates into the internal space 245a of the collet 245. Assoon as the center 242 enters the space 245a, the ring 248 immediatelymoves the claws 247 radially inwardly and into abutment with the lowerend portion or shank 241 of the mandrel 2 30. At the same time, theannular collar 24% of the mandrel 24% which defines a downwardly turnedmotion transmitting shoulder 256 moves into abutment with the upper sideof the stripper 254 and displaces this stripper against the bias of thespring means 255a so that the stripper comes into abutment with theupper end face of the workpiece 52.

In the next step, the operator causes the arbor 244 to move in downwarddirection whereby the lower conical surfaces 259 of the claws 247 moveinto abutment with the upper conical surface 243 of the center 24-2 sothat the claws 247 begin to move radially outwardly and to move theirouter surfaces 257 into abutment with the wall bounding the bore 251 ofthe guide sleeve 250. During the initial stage of the radially outwardlydirected movement of the claws 247 into abutment with the guide sleeve250, the claws continue to perform an axial movement with respect to themandrel 240. In order to reduce friction between the sleeve 251) and theclaws 247, either the claws or the sleeve may be provided with suitablefriction reducing means, not shown, such as spherical or otherwiseshaped rolling elements or the like. The sleeve 250 follows the downwardmovement of the arbor 244 as soon as the outer surfaces 2-57 engage thewall of its bore 251 and is then displaced against the bias of thesprings 252 to the extent determined by the position of the retainingring 253. As soon as the claws 247 are properly retained in the bore251, the mandrel 240 is held against any movement with respect to thesupport 220' and thereby centers the workpiece 52 in requisite positionduring the subsequent gear shaping operation.

The manner in which the workpiece may be released and removed from thedevice of FIGS. 8 and 9 is selfevident. All that is necessary to movethe arbor 244 and the collet 245 in upward direction and to thereuponcause the headstock 54 to move upwardly and away from the workpiece soas to withdraw the mandrel 240 from the stripper 254. i

It was found that the rolling elements of the bearing 2-49 are notsubjected to excessive wear even it they are fitted very tightly betweenthe sleeve 256 and the support 220', as long as their deformation doesnot exceed the elastic limit.

A very important advantage of the clamping devices shown in FIGS. 7 and8 is that they prevent a tilting of the work retaining headstock 54 withrespect to its column 53 or 153, and also that they prevent any tiltingof the column 53 or 153 with respect to the work slide 14. FIG. 1 showsthat the work slide 14, the column 53 and the headstock 54 form asubstantially C-shaped unit which would be likely to open-up in responseto substantial pressure transmitted by the headstock 54 to the worksupport 220, i.e. in which the headstock would be likely to becomemisaligned with its ways 54a or in which the column 53 would tend toassume an inclined position with respect to the work slide 14. Theprovision of a work holding and centering device in which a member (i.e.the arbor 221 of FIG. 7 or the collet 245 of FIG. 8) mounted in the workslide 14 proper cooperates with a complementary member (i.e. the collet225 of FIG. 7 or the mandrel 240 of FIG. 8) which latter is mounted inthe headstock 54 fully eliminates the possibility of any misinclinationof the parts 14, 53 or 153 and 54 with respect to each other because thecollet engages with the respective center and pulls the headstock in adirection toward the spindle nose 51. As a result of such mounting ofthe workpiece 52, the shaving tool 30 may remove comparatively thickshavings from its teeth 52b and the machine may be operated at a veryhigh speed which is possible only if the operator is sure that theposition of the workpiece and/ or of the tool will not change during theactual shaving operation.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic and specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims,

What is claimed as new and desired to be secured by Letters Patent is:

1. In a machine tool, particularly in a gear shaping machine wherein aworkpiece is held by clamping means while subjected to treatment by toolmeans, in combination, a supporting arrangement including a supporthaving elongated ways; a mounting arrangement for mounting one of saidmeans on said supporting arrangement; a headstock for holding the otherof said means, said headstock being reciprocable in said ways toward andaway from said one means; and a reciprocating arrangement for saidheadstock comrpising a motive force-transmitting member operativelyconnected with said headstock and movable in directions enclosing apronounced acute angle with the longitudinal direction of said ways sothat, when said headstock is moved toward said one means, the motiveforce transmitted thereto by said member includes a reciprocating forcecomponent which is parallel with the longitudinal direction of said waysand a pressure force component which is normal to the longitudinaldirection of and is directed against said ways whereby the headstock ispressed against and remains in close contact with said ways along afixed predetermined path to locate said other means in a predeterminedposition and against transversal movement relative to said one means.

2. A structure as set forth in claim 1, wherein said reciprocatingarrangement further comprises a cylinder and piston unit for moving saidmotive force-transmitting member.

3. A structure as set forth in claim 1, wherein said reciprocatingarrangement further comprises mechanical means for moving said motiveforce-transmitting member.

4. A structure as set forth in claim 1, wherein one end of saidmotive-force transmitting member is directly coupled to said headstockand wherein said reciprocating arrangement further comprises operatingmeans for moving said member lengthwise, said operating means beingswingably attached to said supporting arrangement.

5. A structure as set forth in claim 1, wherein said support is a hollowcolumn and wherein at least a portion of said reciprocating arrangementis mounted in said column.

6. A structure as set forth in claim 1, wherein said reciprocatingarrangement further comprises a lever pivotally mounted in said supportand having an arm adjacent to said headstock, and means for pivotingsaid lever with respect to said support, said motive force-transmittingmember comprising a link and a pair of pivot means respectivelyconnecting said link to said headstock and to said arm of said lever.

7. A structure as set forth in claim 1, wherein said mountingarrangement mounts the clamping means and the tool means is mounted onsaid headstock.

8. A structure as set forth in claim 1, wherein said headstock is hollowand said motive force-transmitting member extends into said headstock.

References Cited by the Examiner UNITED STATES PATENTS WILLIAM W. DYER,In, Primary Examiner.

LEON PEAR, Examiner.

1. IN A MACHINE TOOL, PARTICULARLY IN A GEAR SHAPING MACHINE WHEREIN AWORKPIECE IS HELD BY CLAMPING MEANS WHILE SUBJECTED TO TREATMENT BY TOOLMEANS, IN COMBINATION, A SUPPORTING ARRANGEMENT INCLUDING A SUPPORTHAVING ELONGATED WAYS; A MOUNTING ARRANGEMENT FOR MOUNTING ONE OF SAIDMEANS ON SAID SUPPORTING ARRANGEMENT; A HEADSTOCK FOR HOLDING THE OTHEROF SAID MEANS, SAID HEADSTOCK BEING RECIPROCABLE IN SAID WAYS TOWARD ANDAWAY FROM SAID ONE MEANS; AND A RECIPROCATING ARRANGEMENT FOR SAIDHEADSTOCK COMPRISING A MOTIVE FORCE-TRANSMITTING MEMBER OPERATIVELYCONNECTED WITH SAID HEADSTOCK AND MOVABLE IN DIRECTION ENCLOSING APRONOUNCED ACUTE ANGLE WITH THE LONGITUDINAL DIRECTION OF SAID WAYS SOTHAT, WHEN SAID HEADSTOCK IS MOVED TOWARD SAID ONE MEANS, THE MOTIVEFORCE TRANSMITTED THERETO BY SAID MEMBER INCLUDES A RECIPROCATING FORCECOMPONENT WHICH IS PARALLEL WITH THE LONGITUDINAL DIRECTION OF SAID WAYSAND A PRESSURE FGORCE COMPONENT WHICH IS NORMAL TO THE LONTIUDINALDIRECTION OF AND IS DIRECTED AGAINST SAID WAYS WHEREBY THE HEADSTOCK ISPRESSED AGAINST AND REMAINS IN CLOSE CONTACT WITH SAID WAYS ALONG AFIXED PREDETERMINED PATH TO LOCATE SAID OTHER MEANS IN A PREDETERMINEDPOSITION AND AGAINST TRANSVERSAL MOVEMENT RELATIVE TO SAID ONE MEANS.